MOTOR COORDINATIONS. 167 



fixation decrease with repetition, as is shown by the comparison of the 

 two normal days. Comparison of the normal days also shows that as 

 a consequence of practice the duration of the eye-movements increases 

 lightly for both groups of subjects. These two changes are probably 

 to be regarded as causally related. With decreased errors of fixation, 

 the eye-movement sweeps become more nearly full 40 and their dura- 

 tion would naturally increase proportionately. 



If this connection is admitted, the actual angle velocity of the eye- 

 movements appears to have been unaffected by the experimental repeti- 

 tion under otherwise similar circumstances. In spite of the larger errors, 

 however, the adductive movements average slower than the abductive. 

 This difference does not appear to be due to decreased maximum vel- 

 ocity of the eye-movements, but to a proportionately slower third phase, 

 i.e., the final 5 are slower. Any attempt to explain this peculiarity of 

 our subjects would lead us too far from our main problems. 



EFFECT OF ALCOHOL ON THE RECIPROCAL INNERVATION OF 



THE FINGER. 



Eye-movements are not adapted to show the rapidity of free oscil- 

 latory movements of a member, and the consequent speed of alter- 

 nating reciprocal innervations of antagonistic muscles. Successive eye- 

 movements are regularly separated by moments of fixation, seldom 

 less than 0.2" in duration. These are moments of significant vision, 

 for the sake of which the eye-movements exist. True oscillatory move- 

 ments of the eye can not be produced at will without considerable 

 special practice. 



In adopting the reciprocal innervation of the middle finger for meas- 

 uring the speed of alternating reciprocal innervation of antagonistic 

 muscles, we lose the almost ideal conditions with respect to independ- 

 ence of conscious control that obtain in measuring the velocity of the 

 eye-movements. Finger-movements are subject to all sorts of inter- 

 current, facilitating and inhibiting conscious interference. The con- 

 ditions which modify the rate of voluntary reciprocal innervations have 

 not all been experimentally located. In long experiments one will 

 expect warming-up, fatigue phenomena, and spurts of various sorts, 

 as well as lapses of attention and interest, and changes due to subjective 

 feelings of discomfort. (Compare Wells. 1 ) Long-continued finger- 

 movements appear to violate our principle of simplicity at almost as 

 many points as the ergographic experiments. 



These considerations, and practical experience in a series of experi- 

 ments in the fall of 1912, led us to abandon the arrangement of this 

 experiment which was proposed in the program, namely, movements 

 for intervals of 30" followed after 5" by another group of movements 

 for 5". Other things being equal, that would be a most desirable 



Wells, Am. Journ. Psychol., 1908, 19, pp. 345 and 437. 



